Die möglichkeit ist so verdammt alt.
Code:
<style type="text/css">
.u96{visibility:hidden;position:absolute;}
.u96:link{visibility:hidden;position:absolute;left:0px}
.u96:visited{visibility:hidden;left:10px}
.u97{visibility:hidden;position:absolute;}
.u97:link{visibility:hidden;position:absolute;left:0px;}
.u97:visited{visibility:hidden;position:absolute;left:10px;}
</style>
<script>
var url=new Array();
url[0]="http://google.com/";
url[1]="http://free-hack.com/";
var lin;
for (var s=0;s<url.length;s++)
{
    document.write('<a href="'+url[s]+'" class="u96" id="l'+s+'">'+url[s]+'</a>');
    lin=document.getElementById("l"+s);
    if(lin.offsetLeft>0)
    {
        window.document.write("Visitor of "+url[s]+"<br />");
    }
};

</script>